Method for the diagnosis of blood coagulation disorders

An in vitro method for screening and diagnosing activated protein C (APC) resistance which is recognized by a low anti-coagulant response to exogenous activated Protein C (APC) not related to Protein S deficiency or defective FVIII/FVIII.sub.a and recognized by a low anti-coagulant response to exogenous activated Protein C (APC) in the absence of APC immunoglobulin inhibitors

• said method comprising the steps of:
• (i) incubating a human plasma sample from a human in need of screening and diagnosing for APC resistance with
• (1) exogenous APC, or exogenous Protein C and an exogenous reagent that transforms exogenous Protein C to APC;
• (2) an exogenous reagent (I) which at least partially activates a coagulation factor of the blood coagulation system of said human plasma sample;
• and optionally
• (3) an exogenous substrate for an enzyme wherein the activity of said enzyme is influenced by APC, to prepare a final assay medium;
• (ii) measuring a substrate conversion rate for a coagulation factor directly or indirectly activated in step (i), the activity of which is influenced by APC;
• and
• (iii) comparing said substrate conversion rate measured in step (ii) with a standard value obtained from samples of normal individuals, said samples of normal individuals having been subjected to steps (i) and (ii)
• wherein when said substrate conversion rate obtained for said human plasma sample in step (ii) is higher than the standard value, said human has APC resistance.